1. Field of the Invention
The present invention relates to a non-contact type current measuring instrument for measuring an electric current in a live wire in a state of non-contact with the live wire.
2. Description of the Prior Art
A clamp meter that has heretofore been used as a sensor for measuring both an AC and a DC is of a clamp-type in which a conductor to be measured in terms of an electric current is clamped using an opening-closing core for seizing a magnetic flux.
Such a conventional clamp meter requires adoption of a mechanism for opening and closing a core, making its overall structure complicated and resulting in a high manufacturing cost. Furthermore, since the core-opening and -closing operation is required in the current measurement, the measuring work becomes cumbersome.
Moreover, the clamp meter cannot be used in a narrow space where the core for clamping a conductor under measurement is difficult to open. What is worse, there is a possibility of bad measurement being made when the clamping portions of the core are worn off with repeated opening and closing operations.
An open-type current measuring instrument not requiring a core-opening and -closing operation can eliminate the drawbacks of the clamp meter. Because of the measurement accuracy issues, such as errors in measurement due to differences in position of conductors under measurement, reduction in measurement sensitivity to a microcurrent, an influence of an external magnetic field on an open part, etc., however, the open-type current measuring instrument can only measure an AC. In other words, there has been no non-contact type current measuring instrument that can measure both an AC and a DC.
The present invention has been accomplished in view of these circumstances. One object of the invention is to provide a non-contact type current measuring instrument with an open-type core, that can effectively overcome the causes of lowering measurement accuracy including errors in measurement due to differences in position of conductors under measurement and reduction in measurement sensitivity to a microcurrent and can measure both an AC and a DC.
To attain the above object, the present invention provides a non-contact type current measuring instrument comprising an armoring member having a pair of guide portions for a conductor under measurement that form therebetween a guide path with an open end; a magnetic core ring for seizing a magnetic flux that has an open space, is embedded in the armoring member, and comprises a semicircular portion, a pair of straight portions continuous to opposite ends of the semicircular portion and parallel to the guide path and a pair of projecting portions continuous to inside edges of the straight portions and bent so as to face each other and be perpendicular to the guide path; and Hall elements each inserted into and brought into intimate contact with an end face of each of the projecting portions, the conductor being inserted via the open end into the guide path and disposed within the core ring, whereby an electric current passing through the conductor is detected by converging on the core ring a magnetic flux generated by the electric current and utilizing the Hall effect of the Hall elements.
The invention includes a non-contact type current measuring instrument wherein the guide portions have a length from the open end of the guide path to the open space of the core ring that is set to be larger than a length of the open space of the core ring.
The above and other objects, characteristic features and advantages of the present invention will become apparent from the detailed description to be made herein below with reference to the accompanying drawings.